There are several 40mm (wide-angle) enlarging lenses for full-frame 35mm, such as Bogen, Hoya, Yashica, & Osawa Tominon.
There are even more 38mm (wide-angle) enlarging lenses for full-frame 35mm, such as Fujinin-EP, Beslar (from Beseler), Dyotar, Jessop, Durst (from Schneider), & E-Lucky (from Fujimoto).
There's even the amazing 30mm (wide-angle) enlarging lens for full-frame 35mm from Computar (also sold by Kowa).
All of the in-depth reviews of these lenses mention that they have more light fall-off when compared to longer lenses -- just like with regular camera lenses. But stopping down not only eliminates the fall-off problem, you should be stopping down to get better resolution -- just like with regular camera lenses.